Data sources

Study selection

Studies were selected if they were randomised, placebo controlled studies (RCTs) of OTC preparations for acute cough in children
and adults in outpatient settings. RCTs of chronic cough (>3 wks duration), cough resulting from underlying respiratory disease,
or cough induced artificially by inhalation of chemicals were excluded, as were studies of non-oral, herbal, or homeopathic
preparations.

Main results

21 RCTs (n=2604) met the selection criteria. 15 RCTs involved adults (n=2166) and 6 involved children (n=438). Antitussives: in adults, 2 RCTs showed that codeine was not more effective than placebo for reducing cough in adults; 1 RCT found that
dextromethorphan reduced coughing compared with placebo, whereas another found no difference. 1 RCT of moguisteine showed
no difference in cough outcomes except in a subgroup of adults with more severe night cough. The moguisteine group had more
side effects than the placebo group (22% v 8%, p value not reported). 1 RCT (57 children) showed that neither dextromethorphan nor codeine was more effective than placebo
for reducing cough. Expectorants: 1 RCT of guaifenesin in adults showed greater self reported improvement in cough frequency and intensity (75% v 31%, p<0.01). The other RCT showed similar improve-ment in cough in both treatment and control groups, but guaifenesin led
to more adults with reduced sputum thickness (96% v 54%, p=0.001). Mucolytics: in adults, 1 RCT of Bisolvon linctus showed less frequent coughing in the treatment group than in the placebo group (8.6% v 15%, p<0.02). In children, 1 RCT of letosteine showed a mean difference of 0.2 in favour of the letosteine group on a 4 point
symptom scale (p<0.01). Antihistamine decongestant combinations: in adults, 1 study of loratadine/pseudoephedrine showed no difference in cough scores between groups, and another showed
lower severity of cough in the dexbrompheniramine/pseudoephedrine group than in the placebo group (mean score 1.4 v 2.0, p<0.05). In this study, the treatment group had increased dizziness and dry mouth (p≤0.01). In children, 2 RCTs showed
that antihistamine decongestant combinations were not significantly better than placebo for reducing cough. Other drug combinations: EM-VIER was more effective than placebo for reducing cough in adults (reduced coughing fits 25% v 11%, p<0.01; reduced urge to cough 27% v 14%, p<0.01). VICKS MEDINITE was rated as at least “good” for relieving cough by more adults in the treatment group than
in the placebo group (58% v 32%, p<0.01). A dextromethorphan/salbutamol combination improved night time cough compared with placebo or dextromethorphan
alone (mean symptom score 0.19 v 0.67 v 0.44 on d 4, p<0.01). In children, 2 paediatric cough syrups (Triamincol syrup and Dorcol paediatric cough syrup) were not
significantly different from placebo for parental report of satisfactory response. Antihistamines: 3 RCTs in adults showed that antihistamines (terfenadine or thonzylamine) were no better than placebo for resolving cough
symptoms. 1 RCT in children showed that the antihistamines (clemastine and chlorpheniramine) were not better than placebo
for improving cough scores.

COMMENTARY

In the first quantitative review of OTC cold medications, the only significant finding was that combination medications reduced
cough in children 6–12 years of age.1 The review by Schroeder and Fahey used a broad search strategy, and the selection of studies was not constrained by publication
status or language, thus decreasing the risk of inclusion bias.

Schroeder and Fahey selected randomised, placebo controlled studies only and included adults and children. The studies on
children were not stratified according to age group, yet physiological and anatomical differences occur across paediatric
age groups. It is unclear whether the populations in the included studies were generalisable; for example, 1 study included
children from private paediatric clinics.

One of the problems with the literature on OTC medications for cough is that the quality of studies varies, and many have
serious methodological problems (in this review only 5 studies gave any description of the randomisation method).1,2

This review highlights the absence of good evidence, and we can conclude that more research is needed rather than that OTC
cough remedies are ineffective. As a nurse practitioner, I advise patients against the purchase of cough remedies for acute
non-productive cough because cough preparations have no proved efficacy; however, I might consider and suggest an antitussive
if the cough interferes with sleep.